Grout that was not sealed in shower
A friend recently contacted me and asked me for help. He told me that he was watching a home improvement show where they mentioned the importance of sealing shower tile grout. He said that when he and his brother did their tiling a year ago, they never sealed it - he said he never even heard of doing it before. I told him I would help him seal it now if it's the right thing to do. I have a few questions.
1. Is it worth doing after a year has passed?
2. there are some spots on it where it looks like either the grout has worn down, was scrubbed too hard, or was never properly done in the first place. These areas are relatively few, but there is a noticeable dip in the grout there.
He still has some of the grout they used originally. Is it possible to just mix up some grout and go over the old grout to fill in the areas where it is slightly down? Will it bond? Or would we need to remove all the old grout and regrout the entire shower?